This invention relates to building construction adapted for passive solar heating and for a method of designing such construction; and more particularly to modular solar building construction designed to yield economical, yet solar efficient, apartment complexes, condominiums, cluster housing, and the like.
As the world's population increases, and as the world's limited energy resources decrease, there is an ever increasing need for economical, easily constructed, and energy efficient housing. Using energy from the sun to warm buildings (and for other energy needs, such as producing hot water) represents one of the simplest and most practical applications of what is, for all practical purposes, an unlimited energy resource.
Ordinary window glass is the basic material that makes solar heating possible. That is, sunlight passes easily through glass and can be made to strike a darkened surface. A significant portion of the sunlight that strikes such a surface changes from visible light to heat. While the light can be reflected back out again through the glass, the heat is absorbed or trapped by the glass. This phenomenon, which is often termed "the green house effect", is well known in the prior art. In fact, many homes utilize the green house effect through features as simple as a south-facing window. Such a window, at least for houses in the northern hemisphere, admits direct sunlight during most of the day during the winter months of the year when the sun is relatively low in the southern sky. The window glass traps the solar heat, adding warmth to the room where the window is located. The window may be double glazed, thereby enhancing its warming effect because the double glass panes prevent less inside warm air from being lost to the outside and less cold air from infiltrating into the house.
Solar designers and architects have recognized for many years a number of building features that can take similar advantage of solar energy. Such systems, often called "passive systems" (because they require few, if any, mechanical or working parts), are usually an integral part of the building. Accordingly, such systems are most suitable for new construction. A simple passive solar system might include positioning or orienting the building so that the walls and roof receive maximum solar radiation during the winter months of the year. For example, if a house is to be built in a northern hemisphere location (that is, where the sun is relatively low in the southern sky during the winter months of the year), a solar designer may utilize a rectangular structure and place the long axis so that it runs east-west, thereby allowing a southerly exposure for the long side of the building. (The same principle, of course, is applicable for houses built in a southern hemisphere location, where the winter sun is relatively low in the northern sky, thereby encouraging a northerly exposure for the long side of the building.)
Other simple solar features include large window openings on the side of the house exposed to the winter sun, and small windows, or none at all, on the side not exposed to the winter sun. These features serve to maximize solar heat gain and retention of heat in the winter. Unfortunately, even if the windows are double (or triple) glazed, they do not provide an efficient thermal wall for the retention of heat inside the house during the winter (and the retention of cooler temperatures inside the house during the summer). Accordingly, good thermal design requires that a balance be struck between the area of space allocated to windows, the amount of heat that can be gained through the windows during sunny, winter daylight hours, the amount of heat that will be lost through the windows during night-time (or other non-sunlight) hours, and the amount of undesirable heat that will pass through the windows during the hotter summer months of the year. Conventional shaped houses and window placement make this balance (between heat loss and heat gain through windowed areas) extremely difficult to achieve.
Movable shutters and awnings, or fixed overhangs, may be effectively used in the summer to shield excess solar radiation from entering the house. Also, it is to be noted that heavy construction material, such as brick, concrete, stone, or adobe, are favored by solar designers because they provide what is termed "thermal mass." A good thermal mass material positioned within the heated space exhibits the property of absorbing and storing heat, which heat may be released slowly over a long period of time. For example, a concrete or stone wall can be designed to absorb heat during the day and release this heat slowly during the night, thereby helping to moderate the day-night temperature differences.
As explained above, the most efficient solar houses require a lot where a rectangular house may be positioned to maximize exposure to the winter sun, such as by placing the long axis so that it runs east-west. However, not all building lots are favorable for this kind of house orientation. Therefore, if such an unfavorable solar lot is to be used, careful and expensive design of the house must be used to take maximum advantage of available solar energy. Such carefully designed houses, especially with the inflated building and design costs of today's economy, are not affordable for many buyers.
One of the shortcomings of simply placing a window along the side of the structure exposed to the winter sun is that solar energy that enters through such windows is typically trapped within the room where the window is located. Thus, the structure may have rooms along one side that are efficiently warmed (and often over-heated) by the sun's energy, but the remainder of the house is not able to efficiently benefit from this energy. While there are solar systems adapted to transfer this energy throughout the entire house, (such as blowers, fans, or even passive systems such as the "Trombe wall"), these systems are either very expensive or make inefficient use of the available space within the house. Moreover, even if windows are placed along the side of the building exposed to the winter sun, such windows are typically limited in the effective hours during which the sun's rays may pass therethrough. For example, many solar designers feel it is best to orient the windows so that they face slightly to the southeast (for a northern hemisphere location), thereby permitting the building to receive more sunlight earlier in the day when it needs to recover the warmth that has been lost overnight. However, when this is done, then the solar heat that could be gained in the later afternoon hours is lost. Furthermore, even if the window is faced so as to take maximum advantage of both the morning and the afternoon sun, the interior walls of the buildings often limit the penetration depths to which the morning and/or afternoon sun may reach within the structure of the house.
One of the techniques currently used to keep construction costs at a minimum is "modular housing." Modulator housing typically involves square or rectangular modules that are easily assembled, often from prefabricated materials, so as to quickly, efficiently, and economically provide a modest living space. Unfortunately, because economy seems to be the touchstone of such housing, considerations for efficient solar design of modular housing are practically nonexistent.